I bet you these dogs used to bark like crazy whenever someone approached the door. Training an animal to stop doing something is way harder than training an animal to start doing something most of the time. So, solution, train the dogs to start doing something like, say, picking up a pillow whenever someone approaches the door, and as a side effect, they don’t bark at the person because (a) they’re distracted searching for the pillow and (b) it’s kind of hard to bark when you’ve got a pillow in your mouth.